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DRM digital radio services in FM band – Suggested India roadmap

At present, most of the terrestrial radio services (public and commercial) in India are in analogue, except for some services of the public service broadcaster, AIR, in medium wave and shortwaves bands, which are in DRM digital.

Some time back, the broadcasting regulator, Telecom Regulatory Authority of India (TRAI), recommended that digital broadcasting in FM band (VHF band II) should also be allowed, without disturbing the existing analogue transmissions. Recently, the regulator has further recommended the commercial use of low-power terrestrial FM broadcasting for small-range coverage by residential complexes, industrial exhibitions, and small businesses. The licensees should be allowed to deploy any type of transmission technologies (analogue/digital/any other).

DRM digital radio standard for FM broadcasting – The arguments
The DRM Consortium has stressed upon the Indian authorities that the DRM digital radio is the most modern, non-proprietary, and open digital radio standard. It is the only digital radio standard that works in all the radio broadcast bands and some of its benefits are:

  • State-of-the-art future-proof technology. Analogue FM, power and spectrum-hungry, is a 20th-century technology with limited innovation scope. DRM digital broadcasting in the FM band provides multiple services, within the same allocated frequency band, at much-reduced power, along with a host of other value-added services.
  • Half the frequency spectrum required. One audio channel in analogue FM requires a 200 kHz frequency spectrum, whereas one block of DRM digital (which enables the broadcast of up to three audio programs and additional multimedia services like Journaline) requires only 100 kHz, i.e., half the spectrum that is required for an analogue FM transmission.
  • Multiple single audio channels and value-added services. In analogue FM, only one audio program can be broadcast in the allocated 200 kHz bandwidth, whereas DRM digital enables to broadcast of up to three audio programs (and additional multimedia services like Journaline), within just 100 kHz bandwidth.
  • Much lower frequency offset required. In India, center-to-center spacing of 800 kHz is kept between the two analogue FM transmitters (i.e., 600 kHz frequency gap) but a DRM digital transmitter can be installed at a spacing of only a 50 kHz frequency gap from an analogue FM transmission and/or another digital transmitter. Thus, DRM digital permits the operation of many more radio services in digital in the FM band.
  • In addition to excellent audio quality, DRM digital radio offers data services, such as Journaline, SlideShow, etc., which fits use cases, where each audio service can be of a different language while complementing the audio with text and graphics (subtitles, additional info, ads, etc.) on Journaline.
  • Reception in mobile phones. DRM standard is supported natively on all mobile phones, based on the already available tuners for analogue FM reception. No additional hardware and, therefore, no additional design or component cost is required to enable DRM digital FM support on those phones. The DRM app for mobile phones has already been developed. The mobile phone manufacturers need to provide access of the base band digital output to enable reception of DRM digital signals. The mobile phone industry is also expecting a clear policy announcement for India to start incorporating this functionality in future phone models. For legacy phone models, external FM front-end dongles are available. These dongles, along with the already developed DRM radio app, can be used to receive full DRM FM functions.

An efficient and innovative DRM rollout approach in the FM band
The cheapest and easiest way to rollout digital radio services in the FM band is to add a broadband transmitter in every city/town in India, in the unused white space of 600 kHz between the two analogue FM transmitters. The output of this transmitter can be fed to a separate antenna, to be installed on the same tower hosting antennae for the analogue FM transmitters. This transmitter can carry multiple DRM blocks made up of three audio and one valued-added channel.

It is possible to transmit up to five DRM blocks (Fig) in this white space of 600 kHz from a single transmitter. This has been demonstrated successfully by the DRM Consortium in India.

Blocks in white space of 600 kHz between 2 analogue FM transmitters

One DRM block can be assigned to every broadcaster, who will be able to carry up to three high-quality audio services with a lot of value-added services; and will have full control on his content.

If more than five DRM blocks are required per city/town, then two or more transmitters can be installed for DRM digital services. Output of these DRM digital transmitters can be combined and fed to a single antenna.

To sum up
The argument for extending DRM to the FM space in India is that DRM is a high-quality and feature-enhanced digital replacement for the former analogue radio broadcasting standards for AM and FM; as such it can be operated with the same channeling and spectrum allocations as currently employed.

DRM is on-air in India (with over 6 million cars with DRM receivers in the dashboard) and expanding in Asia – with Indonesia, China, and Pakistan adopting DRM. Over the past years, DRM receiver, chipset, and automotive manufacturers have invested significantly to bring down the cost of new receiver models, and to increase their sensitivity and feature completeness. New chipsets and modules are now available, which will enable the production of low-cost Make in India DRM receivers.

The government has already requested all mobile phone manufacturers to provide FM reception, and including the DRM digital as the DRM digital radio reception in the mobile phones is possible without any additional hardware. TRAI has recommended that the Ministry of Information and Broadcasting may constitute a committee to oversee its implementation by the mobile phone manufacturers of FM in mobiles (opening a great opportunity for including DRM as well).

For substantial power saving, excellent sound, efficient use of spectrum, multi-channel provisions, e-learning options, emergency warning functionality, and win-win situation for all the stakeholders, it is hoped that the Government of India will soon announce the policy for the use of DRM in the FM band by the public service broadcaster (AIR/Prasar Bharati), private broadcasters, community radio stations (CRS), and for small-range low-power FM broadcasting.

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